Method of and apparatus for removing pits from metal sheets



Jam-28, 1941. D. E. MULHOLLAND METHOD OF AND. APPARATUS FOR REMvING PITSFROM METAL SHEETS Filed July 12, 1938 5 Sheets-Sheet 1 All 770/50l/a7r0Z Jan. 28 1941.

METHOD OF AND APPARATUS FOR REMOVING FITS FROM METAL SHEETS lllllll D.E. MULHOLLAND 5 Sheets-Sheet 2 3& f f 'I Jan. 28, 1941. D. E. MULHOLLAND 2,230,163

METHOD OF AND APPARATUS FOR REMOVING FITS FROM METAL S HEETS Filed July12, less 5 SheetsSheet s Jan. 28, 1941.

D. E. MULHOLLAND METHOD OF AND APPARATUS FOR REMOVING PITS FROM METALSHEETS 5 Sheets-Sheet 4 Filed July 12, 1938 Jam 1941- D. E. MULLHOLLAND2,230,163

METHOD OF AND APPARATUS FOR REMOVING PITS FROM METAL SHEETS Filed July12, 19 38 5 Sheets-Sheet 5 Patented Jan. 28, 1941 UNITED STATES PATENTOFFICE METHOD OF AND APPARATUS FOR- REMOV- ING PITS FROM METAL SHEETS 7Claims.

This invention relates to a method and apparatus for removing pits inthe surface of metal sheets.

In the manufacture of stainless steel sheets, inclusions ofttimes occurwhich result in voids in the metal at or beneath the surface and thepolishing operations which are necessary to make the sheets acceptableto most industries disclose the presence of such voids or pits as occurat the surface and, unless they are successfully removed, the sheets arerejected.

The present practice of removing the pits involves a hand grindingoperation subsequent to the initial polishing operation. This grindingoperation entails grinding the surface of the sheet over an area havinga radius of three or four inches with the pit as the center, the groundarea being tapered from the outer edge thereof to the bottom of the pit.This tapering is neces sary in order that the reduction in thickness ofthe sheet which is required to remove the pit will not be apparent andit not only results in an appreciable loss of valuable metal butinvolves a highly skilled labor operation. As a sheet may have anywherefrom a few to twenty or thirty pits, the expense of removing them soasto render the sheets commercially acceptable is considerable, not onlyon account of the actual labor cost of the operation and the loss ofmetal, but

also on account of the interruption which it occasions in the flow ofproduction.

The principal object of the present invention is to provide a method andan apparatus whereby pits in the polished surfaces of metal sheets maybe more expeditiously and economically removed. In general, this objectis attained by applying sufficient pressure to the back of the sheet inan area opposed to the pit to be removed to cause metal adjacent thelower portion of the pit to flow toward and flush with the polishedsurface of the sheet.

A primary feature of the invention consists in providing a member forengaging the surface of the sheet surrounding the pit to be removed andmeans for applying pressure to the other surface of the sheet in an areadirectly opposed to the pit for causing metal adjacent the lower portionof the pit to flow'toward said member and flush with the surface of thesheet in engagement therewith.

Another feature of the invention consists in providing opposed membersfor clamping portions of the sheet surrounding the pit to be removed,one of the members having a substantially flat face adapted to engagethe surface of the sheet having the pit and movable means beinassociated with the other of the members for applying pressure to theother surface of the sheet in an area directly opposed to the pit.

Another feature of the invention resides in 5 providing resilient meanspreferably in the form of a rubber plug which is engageable with thesheet in an area directly opposed to the pit to be removed and which iscapable of being subjected to sufficient pressure so as to cause metal10 adjacent the lower portion of the pit to flow toward the surface ofthe sheet having the pit.

Other and more specific features of the invention, residing inadvantageous forms, combinations and relations of parts, willhereinafter ap- .15 pear and be pointed out in the claims.

In the drawings, illustrating a preferred embodiment of the invention,

Figure 1 is a side elevational view of the pit removing machine. 20

Figure 2 is a plan view of the machine.

Figure 3 is a front elevational view of the' machine.

Figure 4 is a vertical sectional view taken on line 4--4 of Figure 2. 25

Figure 5 is a fragmentary vertical sectional view taken on line .55 ofFigure 4.

Figure 6 is a detail View, partly in elevation and partly in section,taken on line B-6 of Figure 4. 30

Figure 7 is a sectional View taken on line of Figure 1.-

Figure 8 is a detail fragmentary sectional view taken on line 8-8 ofFigure 6.

Figure 9 is a plan view of a perforated rubber 35 disk employed in themachine.

Referring more particularly to the drawings,

l' indicates the frame of the machine which may advantageously be formedas a substantially in tegral casting having upper and lower jaws or 40 aparts 2 and 3, respectively. The bottom of the frame may be convenientlyformed with pads or the like l and 5, respectively, which are adapted torest upon and be secured to suitable supports,

such, for example, as I-beams B and I. 45

Rigidly mounted on the forward end of each of the jaw is a cylinder, theone on the upper jaw being designated by the reference numeral 3 and theone on the lower jaw being designated by the reference numeral 9. Eachof the cylin- 50 ders is provided with laterally projecting flanges 10which are rigidly secured as by bolts II to corresponding flanges 12formed integrally with the respective jaws of the frame. To relieve thesecuring bolts I I from shear, each of the cylinders: 5

may be provided with a rearwardly extending rib l3 which fits snuglywithin a suitably shaped recess formed in the front end of the adjacentjaw of the frame.

Movably mounted within the upper cylinder 8 is a hydraulic ram M anddisposed above the ram is a flexible diaphragm l5 which is clampedbetween the cylinder and the head 16, the head being secured to thecylinder by bolts H. The head is provided with a port 18 through whichfluid under pressure from a suitable source, to be hereinafterdescribed, is admitted through a pipe 19 into the cylinder to actuatethe diaphragm l5 and ram Hi. The ram is normally maintained in anelevated position by a spring 20 which is interposed between a shoulder2| formed on the ram and a ledge or shoulder 22 provided on the interiorof the cylinder.

Secured to the lower end of the ram M by a plurality of countersunkscrews or the like 23 is a preferably horizontally disposed plate-likemember 24 which carries a member 25 provided in its lower portion with asteel anvil 25 having a flat bottom surface adapted to engage thesurface of the sheet from which pitsare to be removed. As it isdesirable, for a purpose to be hereinafter explained, to enable themember 25 and the anvil 26 to be moved rearwardly with respect to theram I l, member .25 is slidably connected to the plate-like member 24 bymeans of oppositely disposed channels 21 which are respectively secured,as by bolts 28, to laterally projecting flanges 29 with which the upperportion of member 25 is provided. The upper legs or flanges 353 of thechannels 21 fit within notched-out portions formed in the side edges ofplate member 24, while the lower legs 3| of the channels extend beneaththe lateral flanges 29 of member 25.

Anvil 26 and member 25 are locked or maintained in their normaloperative positions by a pin 32 which is slidably mounted within ahousing whch may be advantageously screw threaded into the web of one ofthe channels 21'. A spring 34 which is disposed within the housing andencircles the pin, normally urges the inner end of the pin into anopening 35 formed in the adjacent flange 29 of member 25, the pinbeingprovided with an annular flange 36 which is adapted to abut againstthe outer edge of flange 29 and affords a shoulder against which thespring 34 bears. The outer end of the pin may be provided with suitablemeans 31 whereby it may be easily retracted to withdraw the inner end ofthe pin from opening 35 and thus enable the anvil and member 25 to moverearwardly. To limit the extent of rearward movement of member 25, theinner end of plate member 24 may be conveniently provided with adepending portion 38.

The inner portion of plate member 24 may also be provided with a pin 39which extends upwardly into an opening 40 formed in the bottom of thecylinder 8. This pin is adapted to move up and down within opening M3 inaccordance with corresponding movements of the ram and it serves toprevent the ram and the parts carried thereby from rotating on avertical axis.

The anvil 26 which fits within a socket formed in the lower end ofmember 25 is removably carried thereby by a ring-like member 4! havingan inwardly projecting annular flange 42 which underlies an outwardlyextending annular'flange d3 formed on the anvil, the ring 4! beingsecured to member 25 by a plurality of screws M. Interposed between theupper end of the anvil and the adjacent portion of member 25 is aperforated rubber disk 45, shown in detail in Figure 9, which enablesthe anvil to angle slightly in order that the bottom face thereof willaccommodate itself to the surface of the sheet which it is intended toengage. Thus regardless of the lack of parallelism of the upper andlower surfaces of the sheet or any deflection which may occur in theframe of the machine due to the loads applied, the rubber disk enablesthe anvil to adjust itself to permit its flat lower surface to bearuniformly upon the adjacent surface of the sheet.

Mounted on the upper end of the lower cylinder is a fixed anvil 4B whichaffords a support for the sheet to be worked upon. The anvil may berigidly and at the same time removably secured to the cylinder by a ringmember 4"! which has an inwardly projecting annular flange 48 adapted tooverlappingly engage an outwardly projecting annular flange 49 on theanvil, the ring being secured to the cylinder by a plurality of screws50. The center of the anvil G6 is provided with a chamber in which arubber plug 54 mounted on the upper end of a plunger 52 is disposed.While the body portion of the plunger may be conveniently made in theform of a cone, the upper portion thereof which projects for a limiteddistance into the chamber in the anvil is of cylindrical shape in crosssection, its diameter being only about .0002 inch less than the diameterof the chamber. This effectively prevents the rubber plug from beingextruded between the plunger and the adjacent part of the anvil and yetprovides the necessary clearance to enable the plunger to move slightlywith respect to the anvil. The rubber plug may, of course, be removablyconnected to the upper end of the plunger, if that is found desirable,and it is to permit inspection of the plug and replacement thereof whenit becomes worn that the upper anvil and member 25 are movablerearwardly with respect to the ram in the upper cylinder.

The plunger 52 has a relatively broad base and seats within a cup-shapedmember 53 disposed within a socket formed in the upper end of a ram 54with which the lower cylinder is provided. The plunger is firmly securedin place by a cap member 55 which is screw threaded on the upper end ofthe ram and is provided with an inwardly projecting annular flange 5.6which overlappingly engages an annular flange 57 on the base of theplunger.

In the lower end'of cylinder 9 is a flexible diaphragm 58 which isclamped in place between the cylinder body and the cylinder head 59, thelatter being provided with a port E0 through which fluid under pressureis admitted from pipe. 6! to actuate the diaphragm and ram, the fluidwhich is delivered to the bottom cylinder being from the same source andunder the same pressure as the fluid delivered to' the upper cylinder.The purpose of the diaphragms in the upper and lower cylinders is toeliminate the use of packing around the rams past which leakage of thefluid under pressure might occur due to the'exceedingly short stroke ofthe ram and the high'pressures involved. Such leakage would, of course,be objectionable on the sheet andwould otherwise interfere with theoperation.

Like the ram of the upper cylinder, the ram of the lower cylinder isprovided with a spring 62 which is interposedbetween the shoulder 63 onthe interior of the cylinder and a shoulder 54 on the ram. Spring 62,however, is stronger than the spring 20 for the ram in the uppercylinder so that, when the pressure, acting on both rams from a commonsource of supply, is released, the lower ram will return to its normalinoperative position a split second before the upper ram returns .andthus prevent the extension of the rubber plug 52 above the top surfaceof the lower anvil.

In the actual practice of removing the pits, circles may be marked onthe sheet around each .of the pits to .be removed as a center, thecircles being made by a pencil or any other suitable means which willnot mar the surface and being preferably of a diameter corresponding tothe diameter of the upper anvil 26. Thus, when the sheet is placed inthe machine between the anvils, the circle serves to locate or positionthe pit to be removed directly above the rubber plug, which isadvantageously of about one-half inch indiameter. The pits occurring inthe sheets may have a diameter of .01 inch or more and a depth of .004inch or .005 inch and may occur in clusters or individually.

The sheets may be conveniently supported on ball top tables, not shown,for delivery to the machine, the tops of the tables being on the samelevel as the upper surface of the lower anvil. When the sheet has beenproperly positioned in the machine between the anvils, fluid underpressure is admitted to the upper cylinder first to move ram l4downwardly and thus cause anvil 26 to rigidly clamp the sheet to anvil46. Pressure is then admitted to the lower cylinder to force the rubberplug 5| into engagement with the back of the sheet in a localized areadirectly opposed to the pit to be removed. The area of the upper ramwhich is subjected to the fluid under presure is greater than the areaof the lower ram subjected thereto and, therefore, a greater total loadwill be exerted by the upper ram on the sheet than will be exerted bythe lower ram. The sheet will, therefore, be firmly held in engagementwith the lower anvil even after'pressure has been admitted to the lowercylinder. By applying pressures of the order of two hundred thousandpounds per square inch, the rubber plug 5| will cause the metal adjacentthe lower portion of the pit to flow upwardly toward the upper anvil 26and flush with the upper surface of the sheet and thus entirelyeliminate the pit. The rubber plug will impart a slight depression tothe back of the sheet where it does no harm and, because of its abilityto conform to any irregularities of the back of the sheet, it willtransmit a uniform pressure and will not make any tool mark on thesheet. The portions of the lower anvil defining the opening in which therubber plug is located furnish a lateral support for the plug andnotwithstanding the magnitude of the pressure to which the plug issubjected, extrusion thereof will not occur between the upper surface ofanvil 4B and the bottom surface of the sheet, because the portions ofthe sheet engaging the upper surface of the anvil will be maintained intight engagement therewith due to the ability of the upper anvil byvirtue of the perforated rubber disk 45 to exert a uniform pressure onall portions of the sheet it engages irrespective of any lack ofparallelism of the upper and lower surfaces of the sheet and anypossible deflection which may occur in the frame of the machine onaccount of the loads involved.

Upon completion of the pit removal operation, the ram of the lowercylinder may be relieved of fluid pressure before the upper ram, inorder that the rubber .plug will not be projected above the top surfaceof the lower anvil, but I have found that, .by providing the lower ramwith a stronger release spring than the upper ram, pressure may berelieved from both rams simultaneously and still the :rubber plug willnot be projected beyond the lower anvil, since the heavier spring actingon the lower ram will serve to cause that ram to return a fraction of asecond before the upper ram returns. strokes of the ram may be madehydraulically by suitably timed pressure means instead of using springs.

The cycle of operation ,of the machine takes place in about five secondsand it will, therefore, .3

be readily apparent that a badly pitted sheet may be completely treatedin from less than a minute to several minutes. As it requires from tento fifteen minutes to remove a single pit by :using the hand grindingmethod heretofore described. which, up to the present time, has beenaccepted as being the most efficient manner of removing pits, thecommercial value of the present invention will be immediatelyrecognized.

While any well known and conventional means may be employed forsupplying fluid under pressure to the cylinders of the machine, there isillustrated in the drawings mechanism which has been found to be wellsuited for that purpose. This mechanism includes a fluid reservoir ortank '65 which may be conveniently located on top of the frame ,of themachine. Mounted on top of the tank is a pump 66 which is preferably ofthe rotary type having an inlet pipe 61 extending downwardly into theliquid within .the tank. The pump maybe driven from any suitable sourceof power, such as an electric motor 68, which may be convenientlymounted on the tank adjacent the pump. The fluid under pressure from thepump passes'thrcugh a pipe 59 to a relief valve i0 which is of suchconstruction that, when the maximum pressure is reached on the pump,excess pump displacement passes from the relief valve back into thesupply tank through pipe 1 I. Normally, however, fluid under pressurefrom the pump passes directly to relief valve '70 and thence through apipe 72 to a four-way valve 13. which is preferably provided with apiston type valve. A check valve M may be located in pipe '!2 to preventthe back flow of fluid to the pump The four-way valve 13 has one portcommunt catingwith pipe 19 through which fluid under pressure isdelivered to the upper cylinder; an other port communicating with pipe15 through which fluid passes to a valve 76 for controlling the flow offluid through pipe 6i into the lower cylinder 9; and another portcommunicating with a pipe 11' through which fluid may flow from thefour-way valve back into the supply tank 65. lhe valve i6 controls therate of flow of the fluid from pipe f5 to pipe BI and it is of suchconstruction that the fluid may not flow therethrough in the reversedirection. There is a by-pass T8, however, around the control valve '16connecting pipes BI and 15 through which the fluid may return from thelower cylinder through the four-way valve to the supply tank, a checkvalve 79 being located within the by-pass to prevent fluid underpressure from passing through the by-pass to the lower cylinder. Thecontrol valve is preferably provided with a port communicating with apipe 80 through which seepage from the valve may return to the supplytank.

The piston valve of the four-way valve 14 is connected to a rod'filwhich is secured at its lower ,If desired, however, the return 10 end toan arm 82 rigidly'mounted upon a rock -shaft 83 which extendslongitudinally of the machine and is journaled in suitable bracketscarried by a beam or the like 84 secured to the I-beam supports 6 and 1of the machine. At its forward end, the shaft 83 is provided with atreadle 85 whereby it may be conveniently rotated by an operator toinduce the desired movement of the piston valve. The rod which connectsshaft 83 with the piston valve is preferably encircled by a spring 86for maintaining the rod as well as the treadle 85 in an elevatedposition.

When the treadle is in its uppermost position, the piston valve is insuch position that pipes l9 and- 15 which respectively lead to the upperand lower cylinders from the four-way valve are in open communicationwith the exhaust pipe 17 leading from the four-way valve to the supplytank. When the treadle is depressed approximately one-half of thedistance it is capable of being moved, the port of the four-way valvecommunicating with pipe I9 is in open communication With the portconnected to pipe 12, but the port of the valve leading to pipe 15remains in open communication with the port leading to pipe 11. Thus,when the treadle is in this position, fluid under pressure is suppliedto the upper cylinder but not to the lower cylinder. When the treadle iscompletely depressed, the position of the piston valve is such thatfluid under pressure is still supplied to the upper cylinder but theport leading to pipe 15 has been opened to communication with pipe 12,while the port leading to the exhaust line 11 has been blocked. Inthisposition of the treadle, therefore, fluid under pressure is suppliedto both cylinders. To release fluid pressure from the cylinders, allthat is required is to relieve the treadle from the force required tooperate it, whereupon the piston valve, as well as its operating parts,will return to its normal position heretofore described.

From the foregoing, it will be perceived that I have devised acomparatively simple method and apparatus for effectively and with aminimum of effort and requiring the exercise of little skill forremoving pits from the polished surfaces of metal sheets. It is manifestthat various modifications may be made in the specific apparatus hereindisclosed to effect this end without departing from the spirit and scopeof the invention as defined in the appended claims.

What I claim is:

l. A machine for removing pits and the like from a metal sheet, saidmachine including a member adapted to engage the surface of the sheetsurrounding the pit, elastic means engageable with the other surface ofthe sheet for applying pressure thereto in an area directly opposed tosaid pit for causing metal adjacent the lower portion of the pit to flowtoward said member and flush with the surface of the sheet in engagementtherewith, and means whereby said elastic means during transmission ofpressure therefrom to said sheet is restrained against deformationotherwise than in conformity to change in the adjacent surface of thesheet.

2. A machine for removing pits and the like from a metal sheet, saidmachine including opposed members for clamping portions of the sheetssurrounding the pit, one of said members having a substantially fiatface adapted to engage the surface of the sheet having the pit, movablemeans including a rubber plug engageable with the other surface of thesheet for applying pressure thereto in an areadirectly opposed to saidpit for causing metal adjacent the lower portion of the pit to flowtoward and flush with the surface of the sheet having the pit,and meanscooperable with the plug during transmission of pressure therefrom tothe sheet for restraining deformation ofthe plug otherwise than inconformity to change in the adjacent surface of the sheet.

. '3. A machine for removing pits and the like from a metal sheet, saidmachine including a member adapted to engage the surface of the sheetsurrounding the pit, a support for the sheet engageable with the othersurface thereof, said member being movable downwardly to clamp the sheetto said support, and means associated with said support for applyingpressure to the surface of the sheet in engagement therewith in an areadirectly opposed to said pit for causing metal adjacent the lowerportion of the pit to flow toward and flush with the surface of thesheet having the pit, said means including anelastic member engageablewith the sheet, said elastic member when applying pressure to thesheetbeing restrained by said support from expanding laterally.

4. A machine for removing pits and the like from a metal sheet, saidmachine including opposed members for clamping portions of the sheetssurrounding the pit, one of said members having a substantially flatface adapted to engage the surface of the sheet having the pit and .toflow toward and flush with the surface'of the sheet having the pit, saidchamber preventing lateral expansion of the elastic means duringtransmission of pressure therefrom to the sheet.

5. A machine for removing pits and the like from a metal sheet, .saidmachine including a sheet supporting member, and means movable towardsaid sheet supporting member for clamping the sheet thereto, said meanscomprising a head having a fiat surface engageable with the surface ofthe sheet having the pit, pressure responsive means for actuating saidhead and resilient means interposed between the fluid pressureresponsive means and the head enabling the flat surface thereof toaccommodate itself to the plane of the surface of the sheet engageablethereby, said supporting means having a chamber adapted to be closed bythe sheet, a rubber member disposed within said chamber, and means forforcing said rubber member into engagement with the adjacent surface ofthe sheet in an area -directlyopposed to the pit to be removed forcausing metal adjacent the lower portion of the pit to flow toward andflush with the surface of the sheet having'the pit, saidchamber'preventing lateral expansion of the rubber member duringtransmission of pressure therefrom to the sheet.

6. A machine for removing pits and the like from ametal sheet, saidmachine including opposed means for clamping portions of thesheetsurrounding the pit, one of said means being engageable with the surfaceof the sheet having the pit, the other of said means comprising a memberengageable with the opposite surface of the sheet and having a chamberadapted to be closed by the sheet, elastic means disposed within saidchamber and being of substantially the same cross sectional area as thelatter, and means movable within said chamber for forcing said elasticmeans into engagement with a portion of the sheet adjacent thereto forcausing metal adjacent the lower portion of the pit to flow toward saidfirst named means and flush with the surface of the sheet in engagementtherewith, said elastic means when applying pressure to the sheet beingrestrained by said chamber against deformation which would increase theprojected area of the portion of the elastic means in engagement withthe sheet.

7. The method of removing pits from the polished surface of a metalsheet which consists in rigidly clamping portions of the sheetsurrounding the pit to be removed, and in forcibly pressing against theback of the sheet within the area of the clamped portion thereof and ina localized area directly opposed to the pit with elastic means which isrestrained against deformation increasing the projecting area thereof inengagement with the sheet whereby metal adjacent the lower portion ofthe pit is caused to flow toward and flush with the polished surface ofthe sheet.

DAVID E. IM'ULHOILAN D.

